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 ln this scheme, each node only depends on itself to detect a black or gray hole. The algorithm does not send out extra control packets so that Routing Packet Overhead  requires no encryption on the control packets to avoid further attacks on detection information sharing  There is no need to watch all neighbors' behavior. Only the next hop in the route path should be observed. As a result, the syste1n performance waste on detection algorithm is lowered. Advantage of the Algorithm

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 When A find B is a BH or GH, A chooses another path. A Path-based Detecting Method: SA D B C Watch dog: SA D B C  When A find B is a BH or GH, A tell S to choose another path.

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 In fig 2, Node S is source node and Node C is destination node.  Packet I is transmitted from Node B to Node C. At the same time, Packet 2 is transmitted from Node S to Node A.  Consequently, Packet 1 and Packet 2 will collide at Node A.  Then Node S will retransmit Packet 2; but Packet 1 will not be sent again because Packet 1 has been received by Node C successfully.  As a result, Node A misses Packet l and treats it being dropped by Node B deliberately. Collision problem

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How do they define whether a node is a gray hole or not? OR(N) collided packets The next node is a gray hole. They use a lot of equations to calculate the drop packets rate, the overheard rate and the collided rate

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 maximum transmission range is 250m  distance between two neighbors is 200m  so that a node can only have 4 neighbors Simulation Results and Discussion

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 Overall Packet Delive1y Rate: the percentage of the data packets which are actually received by the destination.  GM = gray magnitude  Based on this result, we will only focus on gray hole With gray magnitude of 0.6 or above, because a lower gray magnitude cannot bring about great damage to the network